Migraine headache is a complex, recurrent disorder that is one of the most common complaints in medicine. In the United States, more than 30 million people have one or more migraine headaches per year. Approximately 75% of all persons who experience migraines are women.
Migraine was previously considered a vascular phenomenon that resulted from intracranial vasoconstriction followed by rebound vasodilation. Currently, however, the neurovascular theory describes migraine as primarily a neurogenic process with secondary changes in cerebral perfusion. The neurovascular theory holds that a complex series of neural and vascular events initiates migraine.
The theory of cortical spreading depression (CSD) has been advanced to explain the neurologic mechanism of migraine with aura. CSD is a well-defined wave of initial neuronal excitation followed by neuronal silence and then again excitation that returns to normal in cortical gray matter areas that spreads from its site of origin. This transient cellular depolarization is understood to cause the primary cortical phenomenon or aura phase; in turn, it activates trigeminal fibers causing the headache phase. Similar changes are understood to cause pain from migraine with and without aura. CSD is a wave of electrophysiological hyperactivity followed by a wave of inhibition, most often noted in the visual cortex. The scintillating scotoma (visual aura) of migraine in humans may be related to the neurophysiologic phenomenon termed the spreading depression of Leão.
Migraine treatment involves acute (abortive) and preventive (prophylactic) therapy. Patients with frequent attacks may require both. Acute treatments are intended to stop or prevent the progression of a headache or reverse a headache that has started. Preventive treatment, which is given even in the absence of a headache, is intended to reduce the frequency and severity of the migraine attack, make acute attacks more responsive to abortive therapy, and perhaps also improve the patient's quality of life. There remains a need for additional therapies for treating migraine or other neurological disorders.